LASER OPTICAL COATINGS PRODUCED BY ION-BEAM ASSISTED DEPOSITION

A general requirement of optical coatings for lasers is low absorption combined with good mechanical behaviour. Ion beam assisted deposition is recognized to be a technique that gives high density and durable coatings but frequently with unacceptably high absorption. In this work the influence of ion assistance on optical and mechanical properties of films of interest for CO2 laser and excimer laser coatings (MgF2, BaF2, Y2O3, ZrO2, ZnSe) has been investigated. Ion assisted deposited fluorides exhibit a large improvement in hardness and density and at the same time their absorption is low at the wavelengths of interest. The mechanical properties of the other materials are also improved by the ion assistance and, for oxide films, the absorption is lowered by using an oxygen ion beam. Antireflection and partially reflecting coatings for pulsed XeCl (308 nm) and CO2 (10.6-mu-m) lasers have been produced and tested in the operating conditions of the laser resonators where they will be employed.